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Two-stage designs are used widely in Phase II oncology clinical trials to reduce the number of patients placed on ineffective experimental therapies. They provide clear-cut rules for stopping early in the event that treatment is not succeeding as hoped and are relatively simple to implement. Such designs, however, can lead to situations in which patient accrual is continued in the face of a clearly inferior treatment. In situations where patients' response can be determined for many or most subjects before additional patients are enrolled, analyses using Bayesian methodology can lead to earlier termination of studies of ineffective treatments and better align the statistical assessment of treatment effect with the therapeutic objectives of study. These points are discussed in context of the role of Phase II clinical trials in the development of new treatments for cancer.

In spite of the controversy over the role of randomized clinical trials in medical research, the rationale underlying such trials remains persuasive as compared to recent suggestions for alternative non-randomized studies such as those relying on the use of historical controls and adjustment technics. Others have suggested that recent statistical innovations for improving clinical trials, including adaptive allocation of treatment to patients and sequential stopping procedures, are underutilized. These innovations, though theoretically interesting, are not easily adapted to large-scale, complex medical trials in which there may be multiple end points and delayed response times. Ethical considerations suggest that randomized trials are more suitable than uncontrolled experimentation in protecting the interests of patients. Randomized clinical trials remain the most reliable method for evaluating the efficacy of therapies.